An electrochemical measuring cell for detecting hydride gases, especially phosphine and arsine, has become known from EP 436 148 B1. In the prior-art measuring cell, a working electrode, a reference electrode, and an auxiliary electrode are arranged in an electrolyte space of a measuring cell. The electrolyte space is sealed by means of a gas-permeable membrane toward the environment, which contains the gas sample to be measured, which contains the hydride gas to be detected. Sulfuric acid with catalytic additives is used as the electrolyte.
Even though the prior-art measuring cell is characterized by high sensitivity, there are cross sensitivities to a number of other gases. These cross sensitivities are especially disturbing in the case of certain applications, or they may lead to false alarms. Thus, the prior-art measuring cell also responds to NO.sub.2, H.sub.2, C.sub.2 H.sub.2, SO.sub.2, H.sub.2 O.sub.2, and O.sub.3, besides phosphine and arsine.